A wide assortment of endoluminal prostheses have been developed, each providing a uniquely beneficial structure to modify the mechanics of a targeted lumen wall within a body lumen. As used herein, an endoluminal prosthesis is intended to cover a medical device that is adapted for temporary or permanent implantation within a body lumen, including both naturally occurring and artificially made lumens. For example, stent prostheses are known for implantation within body lumens to provide artificial radial support to the wall tissue, which forms the various lumens within the body, and often more specifically, for implantation within the blood vessels of the body. A stent may provide long-term support for damaged or traumatized wall tissues of the lumen or may be implanted, for example, to maintain the patency restored to a blood vessel that was clogged with atherosclerotic plaque. There are numerous conventional applications for stents including cardiovascular, urological, gastrointestinal, and gynecological applications.
Deployment of a stent is accomplished by tracking a catheter through the vascular system of the patient until the stent is located within a target vessel. The treatment site may include target tissue, for example, a lesion which may include plaque obstructing the flow of blood through the target vessel. The stent is expanded or deployed against the vascular wall of the target vessel during or after angioplasty to maintain the opening. Blood flow through the vessel is thereby restored.
However, although relieving a flow constriction in a blood vessel is a primary goal, sudden or abrupt restoration of blood flow may result in reperfusion injury. Reperfusion injury refers to damage to downstream tissue caused when blood supply abruptly returns to the tissue after a period of ischemia. The abrupt restoration of blood flow may shock and overload downstream tissue with high concentrations of oxidative stresses and shear stresses that may cause additional complications such as damage to calcium channels, elevated reactive oxygen species loads, or onset of apoptosis.
Accordingly, a need exists to gradually restore flow and normoxia to ischemic tissue downstream of an obstructive stenosis after an angioplasty procedure. By initially restricting, then gradually restoring blood flow to ischemic tissue, downstream tissue may have time to adapt to the increasing blood flow without incurring reperfusion injury.